The invention relates to a harvester for potatoes, beets and other root crops, comprising a screen conveyor receiving a harvested mix, wherein the screen conveyor has at least one screen conveyor belt that can be supported by lateral guide elements, respectively, wherein at least one conveying stretch positioned at the top and movable opposite to the travel direction of the harvester forms a screening zone that at least in the area of a return pulley that adjoins the leading digging shares can be oriented so as to ascend in the conveying direction.
Machines for harvesting potatoes, beets and other root crops are based on various embodiments of mechanical apparatus with which the harvested crop removed from the soil is separated from entrained admixtures such as stones, soil clods and similar admixed parts. In a system disclosed in DE 10 41 718 the harvested mix is lifted from a soil ridge by means of a digging share and is transferred by a conveying belt into a cleaning stretch with a screen. In a potato harvester according to DE 10 72 422 a screen with a screening chain is provided wherein the latter is moved so as to ascend, beginning at the leading digging share, opposite to the travel direction of the harvester; in this way, separation of the harvested crop from the admixtures is taking place. Similar constructions with a screen that separates the harvested crop from the admixture are disclosed in DE 31 70 73 and DE 66 07 825 as well as DE 23 26 215.
Also known are screen devices for harvesters in which additional movements or excitations are introduced into a respective conveying stretch of the screen conveyor belt so that the separation process is improved in this way. In a system according to EP 0 216 098 B1, the excitation of the screen conveyor belt is achieved by a change of the angular speeds. In a screen conveyor according to DE 94 14 130 U1 the working stretch of the screen conveyor belt that forms the screening zone is provided with inwardly movable adjusting means. These adjusting means, as individual auxiliary elements, are correlated with the conveying stretch that receives the harvested mix so that, by forming at least one “vertical” step, a modified wave-shaped active zone, with a correlated “fall acceleration” of the harvested mix, is provided on the screen conveyor belt. These drop stages that are adjustable with respect to the step height generate a relative movement of the parts of the harvested mix so that separation of soil from the crop is improved but, at the same time, damage of the harvested crop, in particular potatoes, cannot be excluded. The mounted position of the entire screen conveyor belt within the device has a constant incline in the conveying direction.
DE 1 297 731 A1 discloses a potato harvester in which, starting at the digging share, a first screen conveyor belt and a second screen conveyor belt are provided. These two screen conveyor belts interact with each other in the area of an intermediately positioned drop stage. The two conveying belts each define an ascending section with constant incline angle so that the harvested mix is moved upwardly across uniformity ascending screening zones.
The invention concerns the problem of designing a screen conveyor in the area of the respective movable conveying stretch to be adaptable, with minimal technical expenditure, to changing soil conditions such that with a substantially automated modification of the respective conveying conditions a gentle separation of the harvested crop contained in the harvested mix is possible.